Background: Ectopic pregnancy (EP) is the leading pregnancy - related cause of death in the first trimester of pregnancy and a major contributor to maternal morbidity. As the tubal pregnancy progresses, it erodes into blood vessels and can cause massive intra-abdominal bleeding. There are limitations in the strategies currently employed to diagnose EP. Even with the use of diagnostic algorithms that systematically evaluate all women at risk for an EP, only 50 percent of women with an EP can be diagnosed upon presentation. Diagnosis in the remaining 50 percent represents a clinical conundrum and can take up to 6 weeks. If the diagnosis of EP is delayed potential rupture, resulting in greater risks of morbidity and mortality, can occur. Moreover, an EP of large size is not amenable to medical therapy, may require major surgery (laparotomy) instead of laparoscopy and can cause greater damage to fallopian tube (and greater impairment of fertility), even if treated before rupture. This application is a competitive continuing renewal of an ROI (Risk Factors as Predictors of Ectopic pregnancy). We have made substantial progress including delineation of the strength of association of risk factors as predictors, development of a clinical prediction rule to aid in diagnosis upon presentations, and preliminary development of a serum molecular diagnosis using a proteomic approach. We have also redefined the use of serial hCG determinations to diagnosis women at risk for EP whose diagnosis was uncertain at presentation. Finally we have established the safety of a novel medical management regimen for women with ectopic pregnancy. The goals of this application focus on further develop and validation of these finding in a larger, diverse and separate population from which they were developed. Specific Aims and Methods: We plan to extend the systematic evaluation of women at risk for ectopic pregnancy, and collection of serum, form The University of Pennsylvania Medical Center to include to two other centers (The Universities of Miami and Southern California) using a modified existing electronic database that chronicles the clinical course and contains the results of the diagnostic tests used to definitively diagnose women at risk for EP but not diagnosed upon presentation. We plan to use these data to: 1) optimize (and validate) a simple, accurate, non-invasive, diagnosis for the life-threatening condition of ectopic pregnancy using a) clinical factors, b) potential novel serum markers and c) the combination of the two approaches. 2) Identify the proteins that comprise our candidate molecular markers: 3) to validate a decision rule based on serial hCG values for women whose diagnosis was not definitive upon presentation. 4) create a potential test to predict those who will have optimal success with medical management of ectopic pregnancy. This application represents a unique opportunity to combine epidemiologic and basic science methodologies to understand and improve upon important limitations in our ability to diagnose a reproductive disorder with significant public health consequences. We feel that continuation of our translational research has promise to both enhance our understanding of the science of early pregnancy loss as well as to optimize clinical care with potential reduction of morbidity and mortality and therefore fits well into the NIH roadmap strategy to aide interdisciplinary pioneering research to aid in translation from bench to bedside and bedside to practice.